A sub-frame for mounting engines described in Patent Document 1 is exemplified as first background art relating to a frame structure for mounting powerplants. FIG. 15 depicts a sub-frame 103 having a substantially rectangular shape in plan view, which sub-frame is bridged across side frames of a car body so as to mount an engine. In the case where the sub-frame is to be constituted by crossing members 104 and 105 extending widthwise of the car and side members 106 and 107 extending in the fore-and-aft direction of the car body, a plenty of kinds with varied impact energy absorption performance is prepared for the side members 106 and 107, and side members 106 and 107 that are appropriately selected according to modification in the engine or transmission are combined with the crossing members 104 and 105.
A powerplant mounting structure described in Patent Document 2 is exemplified as second background art. As depicted in FIG. 16, this structure is adapted to mount a powerplant member X to the side of a car body with a powerplant supporting member 203 interposed therebetween. While a plurality of types is set for the powerplant member X so as to allow a mounting portion Y to be arranged to the car body side at varied positions in the fore-and-aft direction of the car body, an intermediate bracket 210 is fitted to the mounting portion Y, and the powerplant member X is mounted to the powerplant supporting member 203 with the intermediate bracket 210 interposed therebetween. A plurality of kinds is set for the intermediate bracket 210 with differentiated relative positions of the surface to be fixed to the side of the powerplant supporting member 203 and the surface to be fixed to the side of the mounting portion 205 in the fore-and-aft direction of the car body, so that appropriate one is selected according to the type of the powerplant member X.